The present invention relates in general to a high voltage cable termination, and in particular to a high voltage cable termination for interconnecting a high voltage power source to an X-ray device.
In the use of high voltage equipment, such as an X-ray device, it is often necessary to connect the equipment to a separate power supply with one or more interconnecting cables. The interconnecting cables must be capable of transmitting high voltages, for example in the range of 75,000 to 150,000 volts. Further, the high voltage cable must provide flexibility so as to be able to interconnect power sources and mobile equipment over distances sometimes in excess of 100 feet.
Known high voltage cable terminations often include a number of parts requiring a substantial amount of manual assembly and maintenance. Further, because of the complexity of some known cable terminations, it may not be possible to permit the components to be tested in an assembled state prior to energization. For example, one known high voltage cable termination uses grease between the cable termination and the receptacle port comprising the connector assembly. The grease is intended to displace air in the space between the cable termination and the receptacle to prevent or reduce any high voltage arcing that may occur. However, application of the grease, for example petroleum jelly, is inexact. It is difficult to determine when the grease satisfactorily fills the gap because a serviceperson cannot see into the blind termination. While fluid transformer oil is known to be used similar X-ray cable terminations, the transformer oil use is restricted to installations where the connector assembly is installed, and remains in a vertical position. Attempts to use transformer oil in a tipped or rotated position have been unsuccessful because the termination becomes bulky and unwieldy to accommodate a sealed oil compartment. For example, it is known to include an external oil chamber externally mounted to the cable termination. While the external chamber may account for oil expansion due to temperature changes, the chamber adds to the size of the termination and is subject to damage. Oil-filled terminations often increase costs of fabrication, as well as increase the dimensions of the termination because the termination must account for expansion space for the thermal expansion of the insulating oil. Further, such oil filled terminations include the risk of leakage which affects the environment, and include the potential risk of flashover.
Additionally, high voltage cable terminations are often large and bulky. This creates complications for certain installations. For example, in some hospital applications, the high voltage cable must be pulled considerable distances, sometimes one hundred feet or more, through conduit. Where the cable termination exceeds the diameter of the conduit, the cable must be drawn through the conduit, then subsequently the termination must be installed. Installing the cable termination on-site creates a time consuming process, and quality of cable termination is often degraded. However, many cable terminations that can be assembled and disassembled on site are often difficult to assemble and use. For example, one known cable termination provides a boot that is provided over a cable jacket. Annular grooves are provided along the surface of the boot, arranged to receive a two-piece retainer ring. A nut engages the retainer ring completing the assembly. Alternatively, a two-piece retaining ring is held together by a split ring, provided in an external groove. However, assembling the termination is not easy inside the equipment wall and parts may be dropped causing damage to the equipment. Further, binding might occur as the nut is screwed in place between the nut and the retainer ring, and the retainer ring and the boot.
Accordingly, there is a need for a high voltage cable termination with improved connectivity characteristics that is simple in construction and easy to use.
The present invention overcomes the disadvantages of previously known cable terminations wherein a high voltage cable termination includes a cable wrapped in a dielectric tape, and a braided shield. The shield and dielectric tape are stripped back exposing the conductors. A first, or inner ferrule having a flanged portion and a sleeve portion is slipped over the cable so that the conductors and dielectric tape pass through the inner ferrule and the shield fans out and is slipped over the sleeve portion of the inner ferrule. A second, or outer ferrule is slipped over the sleeved portion of the inner ferrule, and is crimped thereto, thus pinching the shield between the inner and outer ferrules. A pin is crimped to the end of each conductor, and an insulating overmold is applied over the conductors.
In accordance with one embodiment of the present invention, a high voltage cable termination comprises a cable having a first cable end, a plurality of conductors contained in a first insulating material, a dielectric tape wrapping around at least a portion of the conductors, a braided shield wrapped around the dielectric tape, and a cable jacket wrapped around the braided shield. The cable jacket is stripped back from the first cable end exposing a portion of the braided shield, the dielectric tape and the conductors. The braided shield is stripped back from the first cable end exposing a portion of the dielectric tape and the conductors, and the dielectric tape stripped back from the first cable end exposing a portion of the conductors. An inner ferrule has an opening extending entirely therethrough, and includes a flanged portion and a sleeve portion. The inner ferrule is slipped over the cable so that the flanged portion is proximate to the first cable end. The conductors and the dielectric tape extend through the opening, and the braided shield extends over the outside surface of the sleeve portion of the inner ferrule. An outer ferrule is inserted over the sleeve portion of the inner ferrule and crimped thereto, thus pinching the braided shield between the inside surface of the outer ferrule, and the outside surface of the inner ferrule. A pin is secured to the end of each of the plurality of conductors and an insulating material is applied to the exposed portion of the conductors, extending up to the flanged portion of the inner ferrule.
In accordance with another embodiment of the present invention, a high voltage cable termination comprises an inner ferrule having an opening therethrough. A cable has a first cable end, a plurality of insulated conductors and a shield, sheathing at least a portion of the length of the cable. The plurality of conductors run through the opening in the inner ferrule, and the shield wraps around the outside surface of the inner ferrule and an outer ferrule is positioned over the inner ferrule and secured thereto, securing the shield between the inner and outer ferrules.
The inner ferrule preferably comprises a sleeve portion and a flange portion. An opening extends axially through the sleeve portion and exits through the face of the flanged portion. The inner ferrule is installed over the cable such that the flange portion is proximate to the first cable end. Where the opening exits the inner ferrule on the face of the flanged portion, the edge defining the opening may optionally include a chamfer. Secured over the circumference of the sleeve portion, and adjacent to the flanged portion, a key is provided for securing the cable termination once installed in a suitable receptacle. The key is arranged to allow the high voltage cable termination to be lockably securable to the socket or receptacle. The key may be formed in any number of ways, and may optionally include at least one pair of parallel, planar surfaces. The inner ferrule is arranged to form the back end of the cable termination upon being inserted into a receptacle. The flanged portion of the inner ferrule is arranged to guide the cable termination into a corresponding socket. This may be accomplished by providing a contour to the periphery of the opening extending through the inner ferrule along the face of the flanged portion.
The outer ferrule is secured to the inner ferrule, preferably by crimping. The inner and outer ferrules pinch the braided shield creating a solid ground. While the inner and outer ferrules may be constructed of any suitable conductive material, it is preferable that the inner ferrule is constructed of brass, and the outer ferrule is constructed out of aluminum. Further, a pin is electrically coupled to the end of each of the plurality of insulated conductors. Each pin is preferably constructed of brass. The plurality of insulated conductors may include four conductors. As such, the high voltage cable termination comprises a first pin electrically coupled to the end of a first one of the four conductors, a second pin electrically coupled to the end of a second one of the four conductors, and a third pin electrically coupled to the ends of both the third and fourth ones of the four conductors. An overmold of insulating material encases the exposed portion of the conductors. While the overmold may be constructed of any number of suitable insulating materials, it is preferable to construct the overmold from ethylene propylene rubber.
The cable termination may optionally include a semiconductive layer wrapped around the cable under the shield. The semiconductive layer preferably extends underthe inner ferrule, and may be constructed of an extruded layer, or a dielectric tape.
In another embodiment of the present invention, a high voltage cable termination comprises a cable having a first cable end, and four conductors. Each of the four conductors are individually contained in a first insulating material of the cable. A dielectric tape wraps around at least a portion of the conductors, and a braided shield wraps around the dielectric tape. A cable jacket wraps around the braided shield, and serves as a protective outer coating of the shield. The cable jacket is stripped back from the first cable end exposing a portion of the braided shield, the dielectric tape and the conductors. The braided shield is stripped back from the, first cable end exposing a portion of the dielectric tape and the conductors, and the dielectric tape is stripped back from the first cable end exposing a portion of the conductors. An inner ferrule has an opening extending entirely therethrough, and includes a flanged portion and a sleeve portion. The inner ferrule is slipped over the cable so that the flanged portion is proximate to the first cable end, and the conductors and the dielectric tape extend through the opening, and the braided shield extends over the outside surface of the sleeve portion of the inner ferrule. An outer ferrule is inserted over the sleeve portion of the inner ferrule and crimped thereto, thus pinching the braided shield between the inside surface of the outer ferrule, and the outside surface of the inner ferrule.
A first pin is electrically coupled to the end of a first one of the four conductors. A second pin is electrically coupled to the end of a second one of the four conductors, and a third pin electrically coupled to the ends of both the third and fourth ones of the four conductors. An insulating material is applied to the exposed portion of the plurality of conductors, extending up to the flanged portion of the inner ferrule.